Inkjet recording element comprising particles and polymers

ABSTRACT

The invention provides an inkjet recording element comprising a support having thereon an image-receiving layer, said inkjet recording element containing colloidal particles having a charged or chargeable surface and having associated therewith at least two polymers having ionised or ionisable groups thereon, wherein one of those polymers has ionised or ionisable groups of opposite charge to that of the surface of the colloidal particles and another of those polymers has ionised or ionisable groups the same as that of the surface of the colloidal particles. When printed with ink the element can impart good image stability, has a short dry time, can give any required gloss, provides good optical density and is suitable for use with a wide range of inks.

FIELD OF THE INVENTION

The invention relates to an inkjet recording element comprisingcolloidal particles having ionised or ionisable surface groups andpolyelectrolyte species of different charge types.

BACKGROUND OF THE INVENTION

In a typical inkjet et recording or printing system, ink droplets areejected from a nozzle at high speed towards a recording element toproduce an image on the element. The ink droplets, or recording liquid,generally comprise a recording agent, such as a dye or pigment, and alarge amount of solvent. The solvent, or carrier liquid, typically ismade up of water and an organic material such as a monohydric alcohol, apolyhydric alcohol or mixtures thereof

An inkjet recording element typically comprises a support having on atleast one surface thereof an ink-receiving or image-receiving layer, andincludes those intended for reflection viewing, which have an opaquesupport, and those intended for viewing by transmitted light, which havea transparent support.

An important characteristic of inkjet recording elements is their needto dry quickly after printing. To this end, porous recording elementshave been developed which provide nearly instantaneous drying as long asthey have sufficient thickness and pore volume to effectively containthe liquid ink. For example, a porous recording element can bemanufactured by a coating process in which a particulate-containingcoating formulation is applied to a support and is dried. Porousreceivers are usually comprised of colloidal particles with polymericbinders and these absorb ink rapidly through pores that exist betweenthe particles. However, the image stability in these systems is poorwhen exposed to environmental ozone.

Non-porous receivers are usually comprised of one or more polymer layersthat have been coated from solution; because there are no voids in thesestructures, they must swell to absorb the ink. Swelling slows theabsorption and so prints smudge easily after printing. However, oncedried, printed images are often stable when exposed to light or ozone.

Polyelectrolyte multilayers (hereinafter PEMs) consist of particles withtwo or more layers of adsorbed polyelectrolyte species. Each polymerlayer is of opposite charge to the previous layer and the polymers areassociated sequentially via electrostatic attraction. PEMs are wellknown in the literature and a range of uses has been proposed for thesematerials including biosensors or as intermediates in the production ofcontrolled-release drug delivery systems.

Most published PEM technology concerns ‘layer-by-layer coating’ i.e.macroscopic coatings, usually produced by dip coating. WO 96/18498describes using layer-by-layer adsorption for biomedical applications,wherein the layers are adsorbed on macroscopic, polymeric substrates bydip coating. U.S. Patent Application Publication No. 2001/0048975discloses a similar approach, but two polyelectrolytes of oppositecharge are applied in a single coating process by dipping a macroscopicsurface (such as a contact lens) into a pH controlled solutioncontaining two polyelectrolytes. The dip method is not straightforwardlyadapted to colloidal particles.

U.S. Patent Application Publication No. 2000/0002358 describes a methodwhereby a suspension of core/shell nanoparticles is produced. The shellsconsist of an inert material which is used to isolate the functionalcores from their neighbours. These nanoparticles are then coated in amulti stage layer-by-layer dip coating process onto a macroscopic (i.e.not colloidal) substrate to be used for example as magnetic storagedevices.

U.S. Patent Application Publication No. 2002/0187197 and U.S. Pat. No.5,705,222 describe PEMs on the surface of colloidal particles. These maybe prepared from very dilute systems and always require dialysis orsedimentation steps after each polyelectrolyte addition. The extra stepsthat are necessary between every addition of polymer would precludetheir use in economically viable paper coating processes. There is nodisclosure of applicability to inkjet systems. U.S. Pat. No. 6,417,264and German patent application DE 100 33 054 A1 describe methods foradding a single layer of polycation to silica particles with an anionicsurface charge using high pressure mixing. A polyelectrolyte of only onecharge type is used. This combination of a single polyelectrolyte-typewith colloidal particles may be used in inkjet receiving layers.

U.S. Patent Application Publication Nos. 2002/0149656 and 2003/0021983describe the use of PEMs on colloidal particles in inks and otherrecording media for printing onto substrates. These publicationsdescribe recording media containing composites of at least one polymerwith colloidal particles. The composites include colorants or otherfunctional additives. The recording media are applied to a variety ofsubstrates to provide colour to the substrate, to modify the surfacetexture of the substrate or to provide other aesthetic factors. There isno indication that these composites of particles and at least onepolymer could be coated to form part of an inkjet receiving layer; northat the images received into that layer would exhibit enhanced densityor stability to ambient ozone; nor that the receiving layer would beable to provide rapid drying. There is no disclosure of anycommercially-viable method for making inkjet receiver layers ofpractical thickness.

PROBLEM TO BE SOLVED BY THE INVENTION

There is a need to provide an inkjet recording element that, whenprinted with ink can impart good image stability, has a short dry time,can give any required level of gloss, provides good optical densitiesand is suitable for use with a wide range of inks.

SUMMARY OF THE INVENTION

According to the present invention there is provided an inkjet recordingelement comprising a support having thereon at least one image-receivinglayer, said inkjet recording element containing colloidal particleshaving a charged or chargeable surface and having associated therewithat least two polymers having ionised or ionisable groups thereon,wherein one of those polymers has ionised or ionisable groups ofopposite charge to that of the surface of the colloidal particles andanother of those polymers has ionised or ionisable groups the same asthat of the surface of the colloidal particles.

In a further aspect of the invention there is provided a method ofcoating a substrate comprising the steps of

(a) providing colloidal particles having a charged or chargeablesurface;

(b) combining the colloidal particles with at least two polymers havingionised or ionisable groups thereon, one of those polymers havingionised or ionisable groups of opposite charge to that of the surface ofthe colloidal particles and another of those polymers having ionised orionisable groups the same as that of the surface of the colloidalparticles, to provide a coatable formulation;

(c) applying the formulation to the substrate to form a coating thereonand

(d) drying the resultant coating.

In another aspect there is provided the use of the colloidal particlesand associated polymers as hereinbefore described for the preparation ofan inkjet recording element providing enhanced image stability and ashort dry time.

In yet another aspect of the invention there is provided an inkjetprinting method comprising the steps of

(a) providing an inkjet printer that is responsive to digital datasignals;

(b) loading the printer with the inkjet recording element describedabove;

(c) loading the printer with an inkjet composition; and

(d) printing on the inkjet recording element using the inkjetcomposition in response to the digital data signals.

ADVANTAGEOUS EFFECT OF THE INVENTION

The colloidal particles and associated polymers can be coated and driedto form an inkjet recording element that has the required glossiness, istouch-dry after inkjet printing and provides an environment in which thedyes show high stability to ambient ozone.

BRIEF DESCRIPTION OF TIE DRAWINGS

FIG. 1 is a plot of total polyelectrolyte concentration against zetapotential, showing the zeta charge potential of anionic silica particleson sequential addition of polyelectrolytes, wherein

(a) + indicates the addition of varying amounts of 2 kDpolyethyleneimine to silica;

(b) □ indicates the addition of 200 kD sodium polystyrene sulfonate to asilica/2 kD polyethyleneimine composite; and

(c) ● and (d) ◯ indicate composites containing exactly equal amounts ofsilica, 2 kD polyethyleneimine and 200 kD sodium polystyrene sulfonate,with varying amounts of 750 kD polyethyleneimine. However in

(c) ● three polymers were added to silica in three sequential stepswhilst in

(d) ◯ a mixture of 200 kD sodium polystyrene sulfonate with 750 kDpolyethyleneimine was added to a silica/2 kD polyethyleneiminecomposite.

DETAILED DESCRIPTION OF THE INVENTION

The colloidal particles useful in the invention have surface ionised orionisable groups such that the particle has a net anionic or cationiccharge. Particles dispersed in a liquid may gain a surface chargethrough the presence of dissociable groups at the surface by losing acharged species into the bulk liquid, or by adsorption of chargedspecies such as ions, ionic surfactants or ionic polymers in a mannerfamiliar to those skilled in the art or may gain the charge from thepresence of lattice imperfections. Thus the ionised or ionisable groupsmay be an intrinsic part of the particle core, or may be adsorbed,chemically grafted or otherwise attached to the surface. One skilled inthe art can readily determine the conditions favourable for inducing anappropriate charge onto various inorganic or organic particles in such away that they can be used in the present invention.

As used herein the term colloidal particle is defined as a particlewherein one dimension is from 1 nm to 10 μm and hence includes, but isnot limited to, a nanoparticle. The colloidal particles are generallysolid, and may comprise a ‘core’ structure and they are not deformablewhen in the inkjet recording element. Normally they do not impart acolour, other than white, to the element. The particles may be of anyshape but are generally spherical, although they may also becrystalline, rod-, disc- or tube- shaped or pre-aggregated, such asfumed aluminium oxide or a silicon oxide (hereinafter silica).

The equivalent spherical diameter of the colloidal particles,hereinafter ESD, is the diameter of a sphere having a volume equal tothe projected volume. This may be from about 0.01 to about 10 μm,preferably from about 0.02 to about 10 μm, more preferably from about0.04 to about 0.5 μm. Techniques for measuring particle ESD include, butare not limited to, electron microscopy, photon correlationspectroscopy, static light scattering, coulter counter, acoustic sizingtechniques, sedimentation or particle size estimate based upon ameasured surface area for particles of defined geometry, as measured by,for example, the use of a nitrogen absorption isotherm technique. TheESD of the particle can be selected appropriately to the need: forexample increase in ESD will reduce dry time: a decrease in ESD willincrease glossiness.

The colloidal particles may be inorganic or organic or may comprisecomposite materials, the selection of which will be apparent to one ofordinary skill in the relevant art. Any inorganic particles may be used,such as, for example, a silica, silica surface-treated, for example withaluminium and its oxides or molecules with amine or ether groups, analuminium oxide, a clay such as, for example, kaolin, calcined clay,montmorillonite or talc, a magnesium silicate, barium sulfate, calciumcarbonate, calcium oxide, zinc oxide, magnesium oxide, titanium oxide,zirconium oxide, zinc sulfide, a sulfate, carbonate, bicarbonate, oxide,hydroxide, nitrate, boride, carbide, silicide, nitride, phosphide,arsenide, sulfide, selenide, telluride, fluoride, chloride, bromide, oriodide, or halide combination thereof, or an inorganic organic compositesuch as an organo clay. Such materials tend to adopt a negative surfacecharge at high pH and a positive surface charge at low pH.

Organic particles suitable for use in the invention may includepolymeric materials such as, for example, a poly(styrene),poly(methylstyrene), polyurethane, polyacrylate, nylon, polyester,polyamide or poly(melamine formaldehyde) or a combination, derivative orcopolymer thereof. These colloidal particles may obtain a surface chargeby the inclusion of a chargeable monomer or initiator group or by theadsorption of a charged surfactant or polymer.

When the particles are negatively charged, i.e. are anionic, they maysuitably comprise a silica, surface-treated silica, zinc oxide,zirconium oxide, aluminium oxide, a titanium oxide, barium sulfate or aclay such as, for example, kaolin, calcined clay, montmorillonite ortalc. When they are positively charged, i.e. are cationic, they maysuitably include a silica, surface-treated silica, aluminium oxide, zincoxide, magnesium oxide or calcium carbonate.

Preferred colloidal particles for use in the invention are white or‘near-white’ although the invention is not to be considered to be solimited. They may more preferably include a silica, aluminium oxide,talc, barium sulfate, calcium carbonate, kaolin or calcined clay. Mostpreferably the colloidal particles for use in the invention may comprisea silica, such as silica gel, hydrous silica, fumed silica or colloidalsilica The surface of a silica particle may be modified by a range ofmaterials, for example, molecules containing amines or ethers or by theinclusion of aluminium and its oxides. The modification of the silicasurface may be used to change the zeta potential in a manner predictableto one skilled in the art.

Polyelectrolytes, generally, are understood as polymers having chargedor chargeable groups, which can be a component or substituent of thepolymer chain. Usually, the number of these charged or chargeable groupsin polyelectrolytes is so large that the polymers (also called polyions)are water-soluble. The term ‘polyelectrolytes’ is understood in thiscontext to cover also polymers wherein the concentration of charged orchargeable groups within the polymer is not sufficient forwater-solubility. However, the polymers preferably comprisewater-soluble polyelectrolytes. The terms “charged polymer”, “chargeablepolymer” and the term “polyelectrolyte” are, in general, usedinterchangeably herein to include, without limitation, any polymer oroligomer that contains charged or chargeable groups. Polymers with bothanionically and cationically charged or chargeable groups are referredto as polyampholytes and these are specifically included within the term‘polyelectrolyte’. Suitable polyelectrolytes according to the inventionare also biopolymers, modified biopolymers and biopolymer derivatives.

In accordance with this invention at least two polymers, preferably twoor three, are associated with the colloidal particles, eithersequentially and/or as a mixture. Any charged polymer can be used thathas a positive charge, a negative charge or can be induced to carry acharge to provide a net positive or negative charge, for example byadjusting the solution pH.

Synthetic polymers include but are not limited to those that containmonomers which are cationic or which can gain a cationic charge, forexample: allylamine, ethyleneimine, vinylamine, 2-vinylpyridine,4-vinylpyridine, diallyldimethylanmmonium, 2-vinylpiperidine,4-vinylpiperidine, 2-butyl-methacryloxyethyltrimethyl ammonium,4-vinybenzyltrimethylammonium, N,N′-bis2,2,6,6-tetramethyl-4-piperidine, dimethyliminomethylene, butyl acrylatemethacryloxyethyltrimethylammonium and their salts and derivatives.These polymers may be homopolymers of the above monomers or may becopolymers that consist of the above monomers.

Synthetic polymers include but are not limited to those that containmonomers which are anionic or which can gain an anionic charge, forexample: a styrenesulfonic acid, vinylsulfonic acid, acrylic acid,2-acrylamido-2-methyl-propane sulfonic acid, maleic anhydride, maleicacid, ethylene sulfonic acid, methacrylic acid, vinylsulfuric acid,ethylenephosphonic acid, maleic acid, 2-methacryloxyethane-1-sulfonicacid, 3-methacryloxyethane-1-sulfonic acid, vinylbenzoic acid,3-(vinyloxy)propane-1-sulfonic acid, 4-vinylphenol,4-vinylphenylsuiliric acid, 4n-vinylsuccinamic acid and their salts andderivatives. These polymers may be homopolymers of the above monomers ormay be copolymers that consist of the above monomers.

Synthetic polyampholytes include but are not limited to those thatcomprise one or more of the anionic and one or more of the cationicmonomers listed above or may contain monomers which are themselvesamphoteric, for example betaines, sulfobetaines and amino acids.

Biopolymers and their derivatives may include but are not limited topolysaccharides such as chitin, chitosan, xanthan, alginates,carageenans, gummi arabicum, nucleic acids, pectins, proteins such ascasein, albumin, protein derivatives and protein degradation productssuch as gelatins, modified gelatins and gelatin derivatives, as well aschemically modified biopolymers such as carboxymethyl cellulose,carboxyalkyl celluloses, other cellulose derivatives and ligninsulfonates.

Particularly preferred polymers which are cationic or may gain acationic charge for use in the invention include polyethylenimine(hereinafter PEI), poly(4-vinylpyridine) (hereinafter P4VP), and acationically modified polyvinyl alcohol (hereinafter CPVA).

Particularly preferred polymers which are anionic or may gain a anioniccharge for use in the invention include sodium polystyrene sulfonate(hereinafter PSS), others salts of polystyrene sulfonate, copolymersconsisting of styrene sulfonates with other monomers, copolymersconsisting of styrene sulfonates and maleic acid or anhydride monomers,polyacrylic acid (hereinafter PAA), poly 2-acrylamido-2-methylpropanesulfonate and an anionically modifed polyvinyl alcohol (hereinafterAPVA).

A particularly preferred biopolymer for use in the invention is thepolyampholyte gelatin, a modified gelatin or a gelatin derivative.

Depending on the functionality required, a polymer of appropriatemolecular weight can be selected. For example, for mechanical strengthof the dried coating a molecular weight of greater than 20 kD may besuitable. Additionally, for reduction in viscosity of the coating orintermediate formulations, a molecular weight of less than 50 k wouldnormally be used. It may be possible to chemically modify the polymersused so that they include groups which can stabilise dyes against lightfade or ozone fade.

In one embodiment a first polymer associated with the colloidal polymermay contain groups of charge opposite to those on the surface of theparticle. Thus the addition of a polycation such as, for example, PEIwill reduce or reverse the sign of the zeta potential of an anioniccolloidal particle to positive, and addition of a polyanion thereto willcause a further reversal of zeta potential. Alternatively the additionof a polyanion such as, for example PSS, will reduce or reverse the zetapotential of a cationic colloidal particle to negative, and addition ofa polycation thereto will cause a further reversal of zeta potential.

In general, the degree to which the zeta potential of the particles ismodified by the associated polymer or polymers depends upon thecomposition of the polymers, the concentration of the polymers relativeto the surface area of the particles and other factors such as the pH.It is not always necessary nor desirable for each polyelectrolyte toreverse the sign of the zeta potential. If a polyampholyte such asgelatin is the first polymer, the surface charge of the colloidalparticle may be either cationic or anionic.

The zeta potential of the particle with the associated polyampholytedepends upon the composition of the polyampholyte, the concentration ofthe polyampholyte relative to the surface area of the particles and thepH relative to the isoelectric point of the polyampholyte. Where thereis a polyampholyte associated with the particle, a polymer containingpositive or negative chargeable groups may be associated with thecolloidal particle-polyampholyte composite.

It is not always necessary to add each polyelectrolyte in a separatestep. In some cases it may be advantageous to pre-mix polyelectrolytesbefore addition to suspensions comprising the colloidal particles. It isalso a feature of this invention that there is no need for a step toseparate the particles from excess polyelectrolyte, for example betweeneach subsequent addition of polyelectrolyte or polyelectrolytes. Amethod to separate the excess polyelectrolyte would be for exampledialysis, ultrafiltration or sedimentation of the particles followed byremoval of the liquid phase.

The total weight of polymer based upon the volume of the colloidalparticles, may comprise from about 1 to about 500%, preferably fromabout 5 to about 100%, more preferably from about 10 to about 40%. Theamount of poly-electrolyte required depends on the surface area of thecolloidal particles. The figures above are given for spherical particlesof 70-80 nm in diameter. For particles with one or more dimensionssmaller than 70 nm, higher ranges of total polyelectrolyteconcentrations may be desirable.

The ratio of polymer or polymers consisting of groups of one charge tothat of the polymer or polymers consisting of groups of the oppositecharge is normally not limited; however in a preferred embodiment theratio should not be more than about 100 to 1, more preferably 30 to 1and most preferably 5 to 1.

The colloidal particles and associated polymers for use in the inventionare normally located in one or more of the image-receiving layers, whichmay be part of a single or multipart structure. The particles andassociated polymers may also or alternatively be present in an overcoatlayer or an interlayer within the element.

The thickness of the one or more layers containing the colloidalparticles and associated polymers may range from about 1 to about 80 μm,preferably from about 2 to about 40 μm, more preferably from about 3 toabout 30 μm. The coating thickness required is determined through theneed for the coating to act as a sump for absorption of ink solvent andthe need to hold the ink near the coating surface.

In addition to the image-receiving layer and overcoat and interlayer,when present, the recording element may also contain a base layer, nextto the support, the primary function of which is to absorb the solventfrom the ink, but may also contain the colloidal particles andassociated polymers. Materials useful for this layer include particles,polymeric binder and/or crosslinker.

In a preferred embodiment of the invention, the image-receiving layermay contain a binder, in particular a polymeric binder, in an amountsufficient to enhance, where required, mechanical stability or gloss ofthe image-receiving layer. However it is a feature of the invention thata binder is not always necessary to achieve the stated objects of theinvention. The binder may be a hydrophilic polymer such as, for example,a poly(vinyl alcohol), a poly(vinyl acetate) or a latex polymer such as,for example, a styrene acrylic latex or styrene butadiene latex or anyother binder known to the skilled person to be suitable for the purpose.The amount of binder with respect to the colloidal particle can dependon the morphology of particles and the porosity of the structure. Forexample, in the case of spherical particles, the volume ratio ofbinder-to-particle could generally range from 0 to about 0.8, morepreferably from 0 to about 0.6 and most preferably from 0 to about 0.4.The level of binder required may be expected to increase with particleasymmetry or with reduction of particle size.

The support for the inkjet recording element used in the invention maybe any of those usually used for inkjet receivers, such as resin-coatedpaper, paper, polyesters, or microporous materials such as polyethylenepolymer-containing material sold by PPG Industries, Inc., Pittsburgh,Pa. under the trade name of TESLIN™, TYVEK™ synthetic paper (DuPontCorp.), and OPPalyte™ films (Mobil Chemical Co.) and other compositefilms listed in U.S. Patent No. 5,244,861. Opaque supports include plainpaper, coated paper, synthetic paper, photographic paper support,melt-extrusion-coated paper, and laminated paper, such as biaxiallyoriented support laminates. Biaxially oriented support laminates aredescribed in U.S. Pat. Nos. 5,853,965; 5,866,282; 5,874,205; 5,888,643;5,888,681; 5,888,683 and 5,888,714, the disclosures of which are herebyincorporated by reference. These biaxially oriented supports include apaper base and a biaxially oriented polyolefin sheet, typicallypolypropylene, laminated to one or both sides of the paper base.Transparent supports include glass, cellulose derivatives, e.g., acellulose ester, cellulose triacetate, cellulose diacetate, celluloseacetate propionate, cellulose acetate butyrate; polyesters, such aspoly(ethylene terephthalate), poly(ethylene naphthalate),poly(1,4-cyclohexanedimethylene terephthalate), poly(butyleneterephthalate), and copolymers thereof; polyimides; polyamides;polycarbonates; polystyrene; polyolefins, such as polyethylene orpolypropylene; polysulfones; polyacrylates; polyetherimides; andmixtures thereof. The papers listed above include a broad range ofpapers, from high end papers, such as photographic paper to low endpapers, such as newsprint. Additional substrates such as, for example,textiles, wood, metal or plastic may be appropriate, depending upon theproposed application.

In a preferred embodiment, the substrate or support for use in theinvention is paper, resin-coated paper or a transparent support. It mayhave a thickness of from about 50 to about 500 μm preferably from about75 to 300 μm. Antioxidants, antistatic agents, plasticizers and otherknown additives may be incorporated into the support, if desired.

In order to improve the adhesion of the ink-receiving layer to thesupport, the surface of the support may be subjected to acorona-discharge treatment prior to applying the image-receiving layeror layers. Alternatively an under-coating or subbing layer, such as alayer formed from a halogenated phenol or a partially hydrolysed vinylchloride-vinyl acetate polymer, can be applied to the surface of thesupport.

Coating compositions employed in the invention may be applied to one orboth of the substrate surfaces through pre-metered or post-meteredcoating methods. These methods may include dip-coating, wound-wire rodcoating, grooved rod coating, smooth rod coating, air knife coating,bent or bevelled blade coating, gravure coating, forward roll coating,reverse roll coating, multiple roll coating, slide coating, beadcoating, extrusion coating and curtain coating. In those cases where thecoating method permits simultaneous application of multiple layers to asubstrate, the colloidal particles and associated polymers for use inthe invention may be applied as one or more of those layers. Knowncoating and drying methods are described in further detail in ResearchDisclosure No. 308119, published December 1989, pages 1007 to 1008. Thecoating composition can be coated either from water, water-basedmixtures or organic solvents but water is preferred.

The choice of coating process would be determined from the economics ofthe operation and, in turn, would determine the formulationspecifications such as coating solids, coating viscosity and coatingspeed.

In a preferred embodiment the coating formulation would have a coatingof colloidal particles of at least 2% by volume of the coatingcomposition: A more preferred coating composition would containparticles at a concentration of at least 4% by volume and a mostpreferred composition would contain at least 10% by volume colloidalparticles. After application to the substrate, the coating fluids aregenerally dried by simple evaporation, which may be accelerated by knowntechniques such as convection heating. Further treatment, such ascalendaring, may be used to apply a surface texture.

In order to impart mechanical durability to an inkjet recording element,crosslinkers which act upon the colloidal particles and associatedpolymers, or binder, if present, may be added in small quantities. Suchan additive improves the cohesive strength of the layer. Crosslinkerssuch as vinyl sulfones, carbodiimides, polyfunctional aziridines,aldehydes, isocyanates, borax, epoxides and polyvalent metal cations mayall be used.

To reduce colorant fade, UV absorbers, radical quenchers or antioxidantsmay also be added to the image-receiving layer as is well known in theart. Other additives include inorganic or organic particles, pHmodifiers, adhesion promoters, rheology modifiers, surfactants,biocides, lubricants, dyes, optical brighteners, matte agents andantistatic agents. In order to obtain adequate coatability, additivesknown to those familiar with such art, such as surfactants, defoamersand alcohol, may be used. A common level for coating aids is 0.01 to0.30% active coating aid based on the total solution volume. Thesecoating aids can be non-ionic, anionic, cationic or amphoteric. Specificelements are described in McCutcheon's Volume 1: Emulsifiers andDetergents, 1995, North American Edition.

The image-receiving layer(s) employed in the invention can contain oneor more mordanting species or polymers. However an advantage of thepresent invention is that it is not necessary to include a mordant toobtain the benefits of the invention. If present, the mordant polymercan be non-ionic, cationic or anionic, a soluble polymer, a chargedmolecule or a crosslinked dispersed microparticle. Examples of suitablemordants can be found, for example, in U.S. Pat. No. 5,474,843.

Ink jet inks used to image the recording elements of the presentinvention are well-known in the art. The ink compositions used in inkjetprinting typically are liquid compositions comprising a solvent orcarrier liquid, dyes or pigments, humectants, organic solvents,detergents, thickeners and preservatives.

The solvent or carrier liquid can be solely water or can be water mixedwith other water-miscible solvents, such as polyhydric alcohols. Inks inwhich organic materials such as polyhydric alcohols are the predominantcarrier or solvent liquid may also be used. Particularly useful aremixed solvents of water and polyhydric alcohols. The dyes used in suchcompositions are typically water-soluble direct or acid type dyes. Suchliquid compositions have been described extensively in the prior artincluding, for example, U.S. Pat. Nos. 4,381,946; 4,239,543 and4,781,758, the disclosures of which are hereby incorporated byreference.

Although the recording elements disclosed herein have been referred toprimarily as being useful for inkjet printers, they also can be used asrecording elements for pen plotter assemblies. Pen plotters operate bywriting directly on the surface of a recording element using a penconsisting of a bundle of capillary tubes in contact with an inkreservoir. The image-receiving layers may be coated onto a wide range ofsubstrates which can receive an image by a variety of methods.

The invention will now be described with reference to the followingexamples which in no way should be interpreted as restricting the scopethereof

EXAMPLE 1

Schematic Representation of the Formation of PEMs on Colloidal Particles

The following are schematic representations of some ways in which it isenvisaged that the sequential association to a colloidal particle ofpolyelectrolytes may occur, leading to sequential charge reversals andbuild-up of a multilayer. The diagrams are included to assist inunderstanding the invention, without being bound by theory of the actualmechanisms that may be involved. It will also be understood that inaddition to sequential association, for example as represented herein,the polyelectrolytes may alternatively be added as a mixture and notsequentially.

In these diagrams, the polyelectrolytes contain ionised or ionisablegroups. Although the polyelectrolytes are drawn as highly charged, itmay be possible that under the pH conditions of mixing the polymers areessentially uncharged. The addition of a third polyelectrolyte may causecharge reversal of the particle/polymer composite (as shown in theschematic), or it is possible to add a small amount of the thirdpolyelectrolyte, in which case charge reduction rather than reversal mayoccur. In diagram (C) the particle can be positively or negativelycharged. The polyampholyte can be of the same or opposite net charge tothe particle. Polyelectrolyte 1 must contain ionised or ionisablegroups, which can be of the same or opposite charge to the colloidalparticle. Polyelectrolyte 2 must contain ionised or ionisable groups,which must be of opposite charge to polyelectrolyte 1.

EXAMPLE 2

Coating of Particles

(a) Method

The coating formulations were made according to the experimentalprocedures described below. The formulations described all contained 15%w/w silica, corresponding to a volume fraction of 7.43%. Hand coatingswere made from these formulations, with a blade set with a gap of 150 μmonto a 100 μm thick polyethylene terephthalate film with a 50 mg.m⁻² drygelatin ‘subbing’ layer. The film was held on a stainless steel platenby vacuum. Unless indicated the platen was maintained at 30 C bycirculating water. The coatings were dried on the platen at thistemperature, taking up to 45 min. to dry.

Where indicated, stirring was carried out using a magnetic stirrer bar.Filtration was carried out by transferring the sample into a syringe andpassing through a 26 mm diameter cellulose acetate filter (SartoriusMINIART™) with pores of 5 μm diameter.

Each example relied on mixing colloidal suspensions and polymersolutions. The volume ratio (referred to hereafter as Vr) of the twoliquids is expressed asVolume of colloid suspension/Volume of polymer solution.

Unless otherwise stated the colloidal suspensions and polymer solutionswere ‘syringe mixed’. The liquids were taken into graduated syringes,which were then connected to a 90° T-piece junction of internal diameter1.6 mm T-piece via flexible tubing. The liquid was displaced through theT-piece at a rate of approximately 5 ml.s⁻¹. Occasionally it was notpossible to syringe mix the solutions in which case, the solutions were‘addition mixed’. In this procedure a known volume of colloidalsuspension was added to a known volume of polymer solutions whilststirring. The methods indicate where addition mixing was used.

(b) Materials

Materials were used as supplied unless otherwise stated and as indicatedin Table 1. All solutions were made in deionised water. Allconcentrations are expressed as w/w %. TABLE 1 Trade DescriptionSupplier name Other comments Cationic colloidal silica, Ondeo Particlediameter (aluminised surface) Nalco 77 nm* Anionic colloidal silicaGrace LUDOX ™ Particle diameter Davison PW50 77 nm† Polyethyleneimine(PEI) Aldrich 2 kD mean Mw* Polyethyleneimine (PEI) Aldrich 750 kD meanMw* Sodium poly(styrene Alco VERSA ™ 200 kD sulfonate) (PSS) ChemicalTL130 mean Mw* Copolymer of sodium Alco NARLEX ™ 15 kD styrene sulfonateand Chemical D 72 mean Mw* maleic anhydride Copolymer of sodium AlcoVERSA ™ 20 kD Mw* styrene sulfonate and Chemical TL 3 maleic anhydridePoly(4-vinylpyridine Aldrich 60 kD Mw* (P4VP) Anionically derivatisedNippon Gohseran Low degree of poly(vinylalcohol) (APVA) Gohsei L-0302saponification and sulfonic acid modified*. Cationically derivatisedNippon Gohsefimer poly(vinylalcohol) (CPVA) Gohsei K-210 Low gelstrength, de- Eastman calcified lime processed Gelatin ossein gelatinPolyacrylic acid (PAA) Aldrich 2 kD*According to manufacturer's data†Measured using photon correlation spectroscopy(c) Comparison Commercial Samples

Two commercially available materials were tested as supplied.

(i) Porous Receiver

Epson Premium Glossy Photo Paper P-1.

This is a rapid-drying porous inkjet receiver with high gloss but poorozone stability.

(ii) Swellable Receiver

High Gloss Kodak Premium Picture Paper S-1.

This is a polymeric receiver which absorbs ink slowly but has very highgloss and provides images with excellent stability to ozone.

EXAMPLE 3

Analysis of FIG. 1

In the experiments on which FIG. 1 is based the anionic silica used wasLUDOX™ PW50 of particle diameter 77 nm. All materials are fullydescribed in the Table above. In FIG. 1 and the following discussion theamount of polymer present is expressed as percentage weight of polymerper volume of particle. This is a useful measure as it is independent ofthe final particle concentration.

The zeta potential of a particle is a measure of the effective surfacecharge of the particle at the hydrodynamic slipping plane. The zetapotential may be determined from a particle's electrophoretic mobility.Here, the zeta potential was measured with a Malvern Zetasizer 3000HSinstrument. For these measurements, the parent suspensions were dilutedto 0.0500 v/v % (in the absence of polyelectrolyte) or 0.01250 v/v % (inthe presence of polyelectrolyte) silica to avoid multiple scattering.All zeta potential measurements were made with solutions at 0.01 M NaClat 25° C. at pH 6.

The cationic polyelectrolyte 2 kD PEI was added at different levels tothe anionic silica particles (+). A gradual reversal of the zetapotential from negative to positive values with increasing PEIconcentration was apparent. Next, different levels of the anionicpolyelectrolyte, 200 kD PSS were added to the suspensions of 6.75% 2 kDPBI on silica (□). The zeta potential of these PEI-silica particles wasreduced from positive to negative in the presence of increasing amountsof 200 kD PSS.

Then, to suspensions of silica with successively added 6.75% 2 kD PEIand 24.3% 200 kD PSS (the total polyelectrolyte concentration was 31.1%)a second cationic polyelectrolyte (750 kD PEI) was added (●). Additionof the PEI, once again reversed the sign of the zeta potential of theparticles.

The final data shown describe an experiment in which solutions of the200 kD PSS anionic polyelectrolyte with different concentrations of the750 kD PEI cationic polyelectrolyte were added to suspensions of silicawith 6.75% 2 kD PEI. The concentrations of the pre-mixed solutions weredetermined so that the final compositions consisted of 6.75% 2 kD PEIand 24.3% 200 kD PSS with varying amounts of 750 kD PEI on LUDOX™ PW50.These compositions are equivalent to those described in the previousparagraph. The zeta potentials of the particles prepared with thepre-mixed PSS/750 kD PEI solutions (◯) were identical (withinexperimental error) to those where each polyelectrolyte had been addedin a separate stage (●).

EXAMPLE 4

To Investigate ‘Dry Time’ of Prints

(a) Compositions

COMPARATIVE EXAMPLES

P-1 Epson Premium Glossy Photo Paper.

S-1 High Gloss Kodak Premium Picture Paper.

C-1 LUDOX™ PW50, 2 kD PEI

A suspension of 48.18% PW50 was mixed (Vr=1) with a solution of 1.49% 2kD PEI to give a uniform, fluid suspension of 27.73% PW50 and 0.86% 2 kDPEI. After 30 min. this suspension was mixed (Vr=1) with deionised waterto give a uniform, low-viscosity fluid. The final composition of thesuspension was 15% PW50 and 0.46% 2 kD PEI. The sample was held withstirring for 120 min., filtered and stirred for a further 30 min. beforecoating.

C-2 LUDOX™ PW50, 200 kD PSS

A suspension of 27.73% PW50 was mixed (Vr=1) with a solution of 3.62%200 kD PSS to give a uniform, fluid suspension of 15% PW50 with 1.66%200 kD PSS. The resultant suspension was held with stirring for 150 min.then coated.

C-3 LUDOX™ PW50, Gelatin

A suspension of 27.73% PW50 at was mixed (Vr=1) with a solution of 1.17%gelatin to give a uniform, fluid suspension of 15% PW50 with 0.538%gelatin. The resultant suspension was held with stirring for 30 rmin.before coating.

C-4 LUDOX™ PW50, 60kD P4VP

A solution of 3.50% 60 kD P4VP was prepared in 0.3M hydrochloric acid.This solution was mixed (Vr=2.79) with a suspension of 19.80% PW50 togive a uniform, fluid suspension of 15% PW50 with 0.85% 60 kD P4VP. Theresultant suspension was held with stiring for 55 min., filtered andstirred for a further 5 min. before coating.

C-5 LUDOX™ PW50, Gohsefimer K210 (CPVA)

A suspension of 27.73% PW50 was mixed (Vr=1) with a solution of 2.18%CPVA to give a unifoim fluid suspension of 15% PW50 with 1% CPVA. Theresultant suspension was immediately coated.

C-6 Cationic Silica, 200 kD PSS

A suspension of 27.73% cationic silica was mixed (V=1) with a solutionof 3.27% 200 kD PSS to give a uniform, fluid suspension of 15% cationicsilica with 1.5% 200 kD PSS. The resultant suspension was held withstirring for 30 miin. before coating. The suspension was coated onto anddried on a platen held at 45 C.

C-7 Cationic Silica, NARLEX™ 15 kD D72

A suspension of 27.73% cationic silica was mixed (Vr=1) with a solutionof 3.27% 15 kD D72 to give a uniform, fluid suspension of 15% cationicsilica with 1.5% 15 kD D72 The resultant suspension was held withstirring for 30 min. before coating. The suspension was coated onto anddried on a platen held at 45 C.

INVENTIVE EXAMPLES

I-1 LUDOX™ PW50, 2 kD PEI, 200 kD PSS, 750 kD PEI

A suspension of 50% LUDOX™ PW50 was mixed (Vr=1.327) with a solution of2.82% 2 kD PEI to give a uniform, fluid suspension of 32.3% PW50 with1.00% 2 kD PEI. The resultant suspension was held with stirring for 30min. then mixed (Vr=1) with a solution of 4.35% 200 kD PSS to give asuspension of composition 17.71% PW50, 0.55% 2 kD PEI and 1.96% 200 kDPSS. This suspension was held with sting for 60 min., filtered and thenaddition mixed (Vr=5) with 0.76% 750 kD PEI to give a final compositionof 15% PW50, 0.46% 2 kD PEL 1.66% 200 kDPSS and 0.12% 750 kD PEI. Thissuspension was filtered, then held with stirring for lh before coating.

I-2 LUDOX™ PW50 pre-mixed Gohsefimer K-210 (CPVA) and 200 kD PSS

A suspension of 27.73% PW50 was mixed (Vr=1) with a pre-mixed solutionof 0.65% CPVA and 2.42% 200 kD PSS to give a uniform, fluid suspensionof 15% PW50 with 0.3% CPVA and 1.11% 200 kD PSS. The resultantsuspension was held for 1 day with intermittent stirring before beingcoated.

I-3 LUDOX™ PW50, 2 kD PEI Gohseran L-0302 (APVA)

A suspension of 50% PW50 was mixed (Vr=0.9055) with a solution of 1.92%2 kD PEI to give a uniform, fluid suspension of 27.73% PW50 with 0.86% 2kD PEI. The resultant suspension was held with stirring for 30 min. thenmixed (Vr=1) with a solution of 3.27% APVA to give a suspension ofcomposition 15% PW50, 0.463% 2 kD PEI and 1.5% APVA. This suspension washeld with stirring for 30 min. before coating.

I-4 LUDOX™ PW50 Gelatin, pre-mixed 200 KD PSS and 750 KD PEI

A suspension of 50% PW50 at was mixed (Vr=0.9055) with a solution of4.47% gelatin to give a uniform, fluid suspension of 27.73% PW50 with1.99% gelatin. The resultant suspension was held with stirring for 30min. then mixed (Vr=1) with a solution of pre-mixed 3.62% 200 kD PSS and0.25% 750 kD PEI to give a suspension of composition 15% PW50, 1.077%gelatin, 1.66% 200 kD PSS and 0.12% 750 kD PEI. This suspension wasstirred and coated immediately.

I-5 LUDOX™ PW50, 2 kD PEI VERSA™ 2 kD TL3

A suspension of 50% PW50 was mixed (Vr=0.9055) with a solution of 1.92%2 kD PEI to give a uniform, fluid suspension of 27.73% PW50 with 0.86% 2kD PEI. The resultant suspension was held with stirring for 30 min. thenmixed (Vr=1) with a solution of 3.19% 20 kD TL3 to give a suspension ofcomposition 15% PW50, 0.463% 2 kD PEI and 1.47% 20 kD TL3. Thissuspension was held with stirring for 100 min., filtered then stirred 20min. before coating.

I-6 LUDOX™ PW50 2 kD PEI, NARLEX™ 15 kD D72

A suspension of 50% PW50 was mixed (Vr=0.9055) with a solution of 1.92%2 kD PEI to give a uniform, fluid suspension of 27.73% PW50 with 0.86% 2kD PEI. The resultant suspension was held with stirring for 30 min. thenmixed (Vr=1) with a solution of 2.76% 15 kD D72 to give a suspension ofcomposition 15% PW50, 0.463% 2 kD PEI and 1.265% 15 kD D72. Thesuspension was held with stirring for 30 min. before coating.

I-7 LUDOX™ PW50, 2 kD PEI, 2 kD PAA

A suspension of 50% PW50 was mixed (Vr=0.9055) with a solution of 1.92%2 kD PEI to give a uniform, fluid suspension of 27.73% PW50 with 0.86% 2kD PEI. The resultant suspension was held with stirring for 25 min. thenmixed (Vr=1) with a solution of 1.27% 2 kD PAA to give a suspension ofcomposition 15% PW50, 0.463% 2 kD PEI and 0.581% 2 kD PAA. Thissuspension was held with stirring for 25 min. and then coated.

I-8 Cationic Silica, NARLEX™ 15 kD D72, 2 kD PEI

A suspension of 28% cationic silica was mixed (Vr=2.25) with a solutionof 7.31% 15 kD D72 to give a uniform, fluid suspension of 20.33%cationic silica with 2.00% 15 kD D72. The resultant suspension was heldwith stirring for 30 min. then mixed (Vr=2.5) with a solution of 1.31% 2kD PEI to give a suspension of composition 15% cationic silica, 1.478%15 kD D72 and 0.343% 2 kD PEI. This suspension was held with stirringfor 30 min. and then coated.

I-9 Cationic Silica, VERSA™ 20 kD TL3, 2 kD PEI

A suspension of 28% cationic silica was mixed (Vr=2.25) with a solutionof 7.31% 20 kD TL3 to give a uniform, fluid suspension of 20.33%cationic silica with 2.00% TL3. The resultant suspension was held withstirring for 30 min. then mixed (Vr=2.5) with a solution of 1.31% 2 kDPEI to give a suspension of composition 15% cationic silica, 1.478% 20kD TL3 and 0.343% 2 kD PEI. This suspension was held with stirring for30 min. and then coated.

(b) The Ink Transfer Test

The ink transfer test is designed to assess the dry time of the printedimage. A low value of ink transfers would imply a quick dry time. Imageswere printed with an HP Deskjet 970C inkjet printer with thecorresponding HP ink set. The test pattern contained three differentdensities of the colours yellow, magenta, cyan, red, green, blue andblack and a series of black lines and symbols of different size. Thespeed of drying was assessed by assessing the image density transferredto a piece of plain paper that had been pressed manually onto the imageimmediately post printing. A low ink transfer, indicating quickdry-time, is desirable.

(c) Ink Transfer Results

Ink transfer was graded on a scale of 1 to 5. 1=No ink transfer, 2=verylow ink transfer, 3=low ink transfer, 4=medium ink transfer, 5=high inktransfer. TABLE 2 Example Ink Transfer P-1 1 S-1 5 C-1 1 C-2 1 C-3 5 C-43 C-5 5 C-6 3 C-7 2 I-1 3 I-2 2 I-3 2 I-4 1 I-5 2 I-6 1 I-7 1 I-8 2 I-92

The data in Table 2 shows the ink transfer performance of the coatingswherein it can be seen that the commercial porous receiver P-1 showsquick ink, uptake, whilst the commercial swellable receiver S-1 has along drytime, The other comparative examples show behaviour ranging fromno ink transfer to very high ink transfer. The coatings illustrative ofthe invention all show low ink transfer or better (rankings of 3 orless).

EXAMPLE 5

To Investigate Gloss of Coatings

(a) Compositions

COMPARATIVE EXAMPLES

P-1, S-1 and C-1 to C7 as in Example 3

INVENTIVE EXAMPLES

I-1 to I-3 as in Example 3

I-10 LUDOX™ PW50, pre-mixed 2 kD PEI and NARLEX™ 15 kD D72

A suspension of 27.73% PW50 was mixed (Vr=1) with a pre-mixed solutionof 2.76% 15 kD D72 and 1.01% 2 kD PEI to give a uniform, fluidsuspension of 15% PW50 with1.27% 15 kD D72, and 0.46% 2 kD PEI. Theresultant suspension was held with stirring for 87 min., filtered andthen stirred 10 min. before coating.

I-11 Cationic Silica, 2 kD PAA, 2 kD PEI

A suspension of 28% cationic silica was mixed (Vr=2.25) with a solutionof 3.98% 2 kD PAA to give a uniform, fluid suspension of 20.33% cationicsilica with 1.09% 2 kD PAA. The resultant suspension was held withstirring for 30 min. then mixed (Vr=2.5) with a solution of 1.31% 2 kDPEI to give a suspension of composition 15% cationic silica, 0.803% 2 kDPAA and 0.343% 2 kD PEI. This suspension was held with stirring for 30min. and then coated.

I-12 Cationic Silica, 200 kD PSS, 750 kD PEI

A suspension of 28% cationic silica was mixed (Vr=2.25) with a solutionof 7.31% 200 kD PSS to give a uniform, fluid suspension of 20.33%cationic silica with 2.00% 200 kD PSS. The resultant suspension was heldwith stirring for 30 min. then mixed (Vr=2.5) with a solution of 1.31%750 kD PEI to give a suspension of composition 15% cationic silica,1.478% 200 kD PSS and 0.343% 750 kD PEI. This suspension was held withstirring for 30 min. and then coated.

(b) Gloss Test

The gloss of the coating was measured using a ‘Tri-microgloss Meter’(Sheen Instruments Ltd, UK) and the value at 60° used for comparison.Commercial receivers may have different levels of gloss depending upontheir intended use.

(c) Gloss Results

The gloss was rated on a 1-5 scale. 5=matte (gloss=0-10%), 4=satin(gloss=10-25%), 3=soft gloss (gloss=25-40%), 2=glossy (gloss=40-55%),1=super glossy (gloss>55%). TABLE 3 Example Gloss at 60° P-1 3 S-1 1 C-11 C-2 5 C-3 1 C-4 1 C-5 4 C-6 4 C-7 4 I-1 3 I-2 2 I-3 1 I-10 2 I-11 4I-12 5

Usefully, the gloss of the enabling embodiments can vary between any ofthe 5 categories.

EXAMPLE 6

To Investigate Ozone Fade and Density of Printed Images

(a) Compositions

COMPARATIVE EXAMPLES

P-1, S-1 and C-1 to C7 as in Example 4

INVENTIVE EXAMPLES

I-1 to I-4 as in Example 4

I-13 LUDOX™ PW50, 2 kD PEI, premixed 200 kD PSS, 750 kD PEI

A suspension of 48.18% PW50 was mixed (Vr=1) with a solution of 1.49% 2kD PEI to give a uniform, fluid suspension of 27.73% PW50 and 0.86% PEI.The resultant suspension was held with stirring for 30 min. then mixed(Vr=1) with a pre-mixed solution of 3.62% 200 kD PSS and 0.21% 750 kDPEI. The final composition was 15% PW50, 0.46% 2 kD PEI, 1.66% 200 kDPSS, and 0.12% 750 kD PEI. This sample was held with stirring for 120min., filtered, and stirred for a furer 30 min. before coating.

I-14 LUDOX™ PW50, 2 kD PEl, 200 kD PSS

A suspension of 48.18% PW50 was mixed (Vr=1) with a solution of 1.49% 2kD PEI to give a uniform, fluid suspension of 27.73% PW50 and 0.86% 2 kDPEI. The resultant suspension was held with stirring for 30 min. thenmixed (Vr=1) with a solution of 3.62% 200 kD PSS. The final compositionwas 15% PW50, 0.46% 2 kD PEI and 1.66% 200 kD PSS. This sample was heldwith stirring for 120 min., filtered and stirred for a fuirther 30minutes before coating.

I-15 LUDOX™ PW50, Gelatin, 2 kD PEI

A suspension of 48.18% PW50 at was mixed (Vr=1) with a solution of 2.34%gelatin to give a uniform, fluid suspension of 27.73% PW50 with 1.00%gelatin. The resultant suspension was held with stirring for 30 min.then mixed (Vr=1) with a solution of 0.88% 2 kD PEI to give a suspensionof composition 15% PW50, 0.538% gelatin, and 0.405% 2 kD PEI. Thissuspension was held with stirring for 30 min. before coating.

I-16 LUDOX™ PW50, pre-mixed 2 kD PEI and 200 kD PSS

A suspension of 27.73% PW50 was mixed (Vr=1) with a pre-mixed solutionof 3.62% 200 kD PSS and 1.01% 2 kD PEI to give a uniform, fluidsuspension of 15% PW50 with 1.66% 200 kD PSS and 0.46% 2 kD PEI. Theresultant suspension was held with stirring for 110 min., filtered, thenstirred for a further 4 min. before coating.

I-17 LUDOX™ PW50, 60 kD P4VP and 200 kD PSS

A solution of 3.52% 60 kD P4VP was prepared in 0.3M HCl. This solutionwas mixed (Vr=0.906) with a suspension of 50% PW50 to give a uniform,fluid suspension of 27.73% PW50 with 1.57% 60 kD P4VP. The resultantsuspension was held with stirring for 30 min. then mixed (Vr=1) with asolution of 3.62% 200 kD PSS to give a suspension of composition 15%PW50, 0.848% 60 kD P4VP and 1.663% 200 kD PSS. This suspension was heldwith stirring for 30 min. before coating.

(b) Assessment of Initial Image Density and Image Stability to Ozone

To assess image stability to ozone, cyan, magenta and yellow patcheswere printed with a Kodak Personal Picture Maker 200 inkjet printer andcorresponding Kodak ink-set. The images were allowed to dry overnightthen the initial colour densities measured. The status A print densitieswere measured with a X-rite™ 310 Colour Transmission/ReflectionDensitometer (X-rite company) The printed images were placed in anenvironment with a high level of ambient ozone (approximately 5 ppm).The loss in image density after 24 h was assessed by re-measuring thestatus A print densities. A sample of comparative sample papers S-1 andP-1 was always present alongside the experimental samples for comparisonto allow for any variation in ozone levels. A high initial image densityand a low loss in density on exposure to ozone is desirable.

(c) Image Stability to Ozone Results The fade was rated on a 1-5 scale.1=very low or no fade, 2=low fade, 3=medium fade, 4=high fade, 5=veryhigh fade. The yellow fade was always very low or less. The initial inkdensity is the measured status A density. TABLE 4 Fade after exposure toozone Cyan Initial ink density Example ink Magenta ink Cyan ink Magentaink Yellow ink P-1 4 4 0.600 0.920 1.060 S-1 1 1 0.744 0.865 0.942 C-1 53 0.663 1.117 1.200 C-2 4 3 0.843 1.087 1.322 C-3 5 5 0.810 1.170 1.330C-4 3 5 0.687 1.111 1.613 C-5 5 4 0.639 1.064 1.252 C-6 5 5 0.966 1.2391.462 C-7 5 5 0.958 1.188 1.295 I-1 2 1 0.772 1.210 1.340 I-2 3 2 0.8911.166 1.441 I-3 3 2 0.862 1.097 1.351 I-4 2 2 0.893 1.257 1.628 1-13 2 20.814 1.236 1.415 1-14 1 1 0.708 1.184 1.366 1-15 2 3 0.890 1.190 1.2801-16 2 1 0.875 1.226 1.467 1-17 3 3 0.815 1.102 1.208

The commercial receiver S-1 showed excellent resistance to ozone fade;however, the porous commercial receiver P-1 was not effective atpreventing ozone fade. The other comparative examples all show high fadelevels. The enabling embodiments all gave significantly better faderesistance than P-1, with some samples giving comparable performance toS-1.

In addition to the ozone behaviour, the initial print densities of theenabling embodiments are advantageously higher than that of thecommercial receivers and of the same order as those of the othercomparative receivers. The coating I-14 has a slightly lower initialcyan density, but significantly higher magenta and yellow densities thanthe commercial receivers and comparable densities to the comparativeexamples.

(d) Combination of Fast Dry Time and Ozone Fade Resistance

Ink transfer was graded on a scale of 1 to 5. 1=No ink transfer, 2=verylow ink transfer, 3=low ink transfer, 4=medium ink transfer, 5=high inktransfer. Low ink transfer is desirable.

The fade was rated on a 1-5 scale. 1=very low or no fade, 2=low fade,3=medium fade, 4=high fade, 5=very high fade. The yellow fade was alwaysvery low or less. Low ozone fade is desirable. TABLE 5 Example InkTransfer Cyan fade Magenta fade P-1 1 4 4 S-1 5 1 1 C-1 1 5 3 C-2 1 4 3C-3 5 5 5 C-4 3 3 5 C-5 5 5 4 C-6 3 5 5 C-7 2 5 5 I-1 3 2 1 I-2 2 3 2I-3 2 3 2

The porous commercial receiver P-1 shows short dry times with poorresistance to ozone fade. Conversely, the swellable commercial receiverS-1 shows long dry times with good resistance to ozone fade. Theelements for use in the invention I-1 to I-3 show an advantageouscombination of shorter drytimes than the commercial swellable receiverS-1 with less ozone fade than the commercial porous receiver P-1. Thecomparative examples C-1 to C-7 do not show this combination ofproperties. In addition, it is shown in examples 5 and 6 that enablingembodiments have a higher initial ink density than the commercialmaterials, and can be made with any level of gloss.

EXAMPLE 7

To Investigate Ozone Fade of Printed Images with the Epson Ink Set

In These Examples the Silica used was LUDOX™ PW50, Particle Diameter 65nm

(a) Compositions

COMPARATIVE EXAMPLES

P-1, S-1 as in Example 4

C-8. LUDOX™ PW50, 2 kD PEI

A suspension of 27.7% PW50 was mixed (Vr=1) with a solution of 1.20% 2kD PEI to give a uniform, fluid suspension of 15.0% PW50 and 0.55% 2 kDPEI. The resultant suspension was held with stirring for 180 min.,before coating.

INVENTIVE EXAMPLES

I-18 LUDOX™ PW50, 2 kD PEI 200 kD PSS, 2 kD PEI

A suspension of 27.7% PW50 was mixed (Vr=1) with a solution of 1.20% 2kD PEI to give a uniform, fluid suspension of 15.0% PW50 and 0.55% 2 kDPEI. The resultant suspension was held with stirring for 1 h thenaddition mixed (Vr=11.49) with 29.92% 200 kD PSS to give a uniform fluidsuspension of composition 13.89% PW50, 0.51% 2 kD PEI and 2.21% 200 kDPSS. The resultant suspension was held with stirring for 1 h thenaddition mixed (Vr=31.17) with 25.35% 2 kD PEI to give a finalcomposition of 13.49% PW50, 0.49% 2 kD PEI 2.15%200 kD PSS and 0.73% 2kD PEI.

(b) Assessment of Initial Image Stability to Ozone Using an EpsonPrinter.

To assess image stability to ozone, cyan, magenta and yellow patcheswere printed with an Epson Stylus Photo 870 inkjet printer andcorresponding Epson ink-set. The images were allowed to dry then theinitial colour densities measured. The status A print densities weremeasured with an X-rite™ 310 Colour Transmission/Reflection Densitometer(X-rite company). The printed images were placed in an environment witha high level of ambient ozone (approximately 5 ppm). The loss in imagedensity after 24 h was assessed by re-measuring the status A printdensities. A sample of comparative sample papers S-1 and P-1 was alwayspresent alongside the experimental samples for comparison to allow forany variation in ozone levels. A low loss in density on exposure toozone is desirable.

(c) Image Stability to Ozone Results

The fade was rated on a 1-5 scale. 1=very low or no fade, 2=low fade,3=medium fade, 4=high fade, 5=very high fade. The yellow fade was alwaysvery low or less. TABLE 6 Fade after exposure to ozone Example Cyan inkMagenta ink P-1 4 5 S-1 1 2 C-8 1 4 I-18 1 1

The commercial receiver S-1 showed excellent resistance to ozone fade;however, the porous commercial receiver P-1 was not effective atpreventing ozone fade. The other comparative example performedrelatively well with this ink set, exceeding the performance of P-1.However, the embodiment for use in the invention gave better faderesistance than both P-1 and S-1. This example illustrates that thebenefits of the invention are not limited to a single ink set.

The invention has been described in detail with particular reference topreferred embodiments thereof, but it will be understood that variationsand modifications can be effected within the scope and spirit of theinvention.

According to the present invention there is provided an inkjet recordingelement comprising a support having thereon at least one image-receivinglayer, said inkjet recording element containing colloidal particleshaving a charged or chargeable surface and having associated therewithat least two water-soluble polymers having ionised or ionisable groupsthereon, wherein one of those polymers has ionised or ionisable groupsof opposite charge to that of the surface of the colloidal particles andanother of those polymers has ionised or ionisable groups the same asthat of the surface of the colloidal particles.

Please replace the paragraph beginning on page 4, line 6 with thefollowing rewritten paragraph:

(b) combining the colloidal particles with at least two water-solublepolymers having ionised or ionisable groups thereon, one of thosepolymers having ionised or ionisable groups of opposite charge to thatof the surface of the colloidal particles and another of those polymershaving ionised or ionisable groups the same as that of the surface ofthe colloidal particles, to provide a coatable formulation;

Please replace the paragraph beginning on page 7, line 23 with thefollowing rewritten paragraph:

Polyelectrolytes, generally, are understood as polymers having chargedor chargeable groups, which can be a component or substituent of thepolymer chain. The number of these charged or chargeable groups inpolyelectrolytes is so large that the polymers (also called polyions)are water-soluble. The terms “charged polymer”, “chargeable polymer” andthe term “polyelectrolyte” are, in general, used interchangeably hereinto include, without limitation any polymer or oligomer that containscharged or chargeable groups. Polymers with both anionically andcationically charged or chargeable groups are referred to aspolyampholytes and these are specifically included within the term‘polyelectrolyte’. Suitable polyelectrolytes according to the inventionare also biopolymers, modified biopolymers and biopolymer derivatives.

Please replace the paragraph beginning on page 8, line 6 with thefollowing rewritten paragraph:

In accordance with this invention at least two water-soluble polymers,preferably two or three, are associated with the colloidal particles,either sequentially and/or as a mixture. Any charged polymer can be usedthat has a positive charge, a negative charge or can be induced to carrya charge to provide a net positive or negative charge, for example byadjusting the solution pH.

1. An inkjet recording element comprising a support having thereon atleast one image-receiving layer, said inkjet recording elementcontaining colloidal particles having a charged or chargeable surfaceand having associated therewith at least two water-soluble polymershaving ionised or ionisable groups thereon, wherein one of thosepolymers has ionised or ionisable groups of opposite charge to that ofthe surface of the colloidal particles and another of those polymers hasionised or ionisable groups the same as that of the surface of thecolloidal particles.
 2. An element as claimed in claim 1 wherein thecolloidal particles are organic, inorganic or a composite thereof.
 3. Anelement as claimed in claim 1 wherein the colloidal particles arenegatively charged and are selected from the class consisting of asilica, surface-treated silica, zinc oxide, zirconium oxide, aluminiumoxide, titanium oxide, barium sulfate, kaolin clay, calcined clay,montmorillonite and talc.
 4. An element as claimed in claim 1 whereinthe colloidal particles are positively charged and are selected from theclass consisting of a silica, surface-treated silica, aluminium oxide,zinc oxide, magnesium oxide and calcium carbonate.
 5. An element asclaimed in claim 1 wherein the particles are colloidal silica, silicagel, hydrous silica or fumed silica.
 6. An element as claimed in claim 1wherein the equivalent spherical diameter of the colloidal particles isfrom about 0.01 to about 10 μm.
 7. An element as claimed in claim 6wherein the equivalent spherical diameter of the colloidal particlesdiameter is from about 0.04 to about 0.5 μm.
 8. An element as claimed inclaim 1 wherein a polymer includes a monomer that has a positive chargeor can be induced to have a positive charge and is independentlyselected from the class consisting of allylamine, ethyleneimine,vinylamine, 2-vinylpyridine, 4-vinylpyridine, diallyldimethylammonium,2-vinylpiperidine, 4-vinylpiperidine, 2-butyl-methacryloxyethyltrimethylammonium, 4-vinybenzyltrimethylammonium, N,N′-bis2,2,6,6-tetrainethyl-4-piperidine, dimethyliminomethylene, butylacrylate methacryloxyethyltrimethylammonium and a salt or derivativethereof.
 9. An element as claimed in claim 1 wherein a polymer isselected from polyethyleneimine, poly(4-vinylpyridine) andcationically-modified polyvinyl alcohol.
 10. An element as claimed inclaim 1 wherein a polymer includes a monomer that has a negative chargeor can be induced to have a negative charge and is independentlyselected from the class consisting of styrenesulfonic acid,vinylsulfonic acid, acrylic acid, 2-acrylamido-2-methyl-propane sulfonicacid, maleic anhydride, maleic acid, ethylene sulfonic acid, methacrylicacid, vinylsulfuric acid, ethylenephosphonic acid, maleic acid,2-methacryloxyethane-1-sulfonic acid, 3-methacryloxyethane-1-sulfonicacid, vinylbenzoic acid, 3-(vinyloxy)propane-1-sulfonic acid,4-vinylphenol, 4-vinyl-phenylsulfuric acid, 4-n-vinylsuccinamic acid anda salt or derivative thereof.
 11. An element as claimed in claim 1wherein a polymer is selected from the class consisting of a sodiumpolystyrene sulfonate, a polystyrene sulfonate salt, a copolymer ofstyrene sulfonate with another monomer, a copolymer of styrenesulfonates and a monomer of maleic acid or anhydride monomer,polyacrylic acid, poly 2-acrylamido-2-methyl-propane sulfonate and ananionically-modifed polyvinyl alcohol.
 12. An element as claimed inclaim 1 wherein a polymer comprises a styrenesulfonate monomer.
 13. Anelement as claimed in claim 1 wherein a polymer is a polyampholytecopolymer comprising a mixture of uncharged and pH-dependent negativeand positive charges.
 14. An element as claimed in claim 13 wherein thepolyampholyte is gelatin or a gelatin derivative.
 15. An element asclaimed in claim 1 wherein the total weight of polymer based upon volumeof the colloidal particles is about 10 to about 40%.
 16. An element asclaimed in claim 1 wherein the ratio of a polymer or polymers of onecharge type to that of another polymer or polymers of another chargetype is not more than about 100:1.
 17. An element as claimed in claim 1wherein the image-receiving layer contains a binder selected from theclass consisting of a poly(vinylalcohol), poly(vinyl acetate), styreneacrylic latex and styrene butadiene latex.
 18. An element as claimed inclaim 1 wherein the image-receiving layer contains one or more mordants.19. A method of coating a substrate comprising the steps of (a)providing colloidal particles having a charged or chargeable surface:(b) combining the colloidal particles with at least two water-solublepolymers having ionised or ionisable groups thereon, one of thosepolymers having ionised or ionisable groups of opposite charge to thatof the surface of the colloidal particles and another of those polymershaving ionised or ionisable groups the same as that of the surface ofthe colloidal particles to provide a coatable formulation; (c) applyingthe formulation to the substrate to form a coating thereon and (d)drying the resultant coating.
 20. A method as claimed in claim 19wherein the at least two polymers are added either sequentially and/oras a mixture.
 21. (canceled)
 22. (canceled)
 23. A method as claimed inclaim 19 wherein the substrate is paper, resin-coated paper or atransparent support.
 24. A method as claimed in claim 19 wherein theformulation is coated onto the substrate by a pre-metered orpost-metered coating method.
 25. A method as claimed in claim 19 whereinthe coating formulation comprises at least 4% by volume of colloidalparticles.
 26. The use of colloidal particles to provide an inkjetelement providing improved image stability and dry time having a chargedor chargeable surface and at least two polymers having ionised orionisable groups thereon to provide an inkjet recording elementcomprising a support having thereon at least one image-receiving layer,said inkjet recording element containing said colloidal particles andhaving associated therewith said at least two water-soluble polymers,wherein one of those polymers has ionised or ionisable groups ofopposite charge to that of the surface of the colloidal particles andanother of those polymers has ionised or ionisable groups the same asthat of the surface of the colloidal particles.
 27. An inkjet printingmethod comprising the steps of (a) providing an inkjet printer that isresponsive to digital data signals; (b) loading the printer with aninkjet recording element comprising a support having thereon at leastone image-receiving layer, said inkjet recording element containingcolloidal particles having a charged or chargeable surface and havingassociated therewith at least two water-soluble polymers having ionisedor ionisable groups thereon, wherein one of those polymers has ionisedor ionisable groups of opposite charge to that of the surface of thecolloidal particles and another of those polymers has ionised orionisable groups the same as that of the surface of the colloidalparticles; (c) loading the printer with an inkjet composition; and (d)printing on the inkjet recording element using the inkjet composition inresponse to the digital data signals.